1. Field of the Invention
This invention relates to tandem axle assemblies and, in particular, to a tandem axle assembly designed to accommodate variations in length along the vehicle driveline during movement of a vehicle.
2. Discussion of Related Art
A conventional tandem axle assembly includes forward and rear axle assemblies and an intermediate drive shaft assembly connecting the two axle assemblies. The forward and rear axle assemblies each include a pair of axle half shafts extending therefrom on which one or more wheels of a vehicle are mounted. Each of the forward and rear axle assemblies further include a differential that allows the vehicle wheels on each axle assembly to rotate at different speeds. Each of the differentials includes a pinion gear in mesh with a ring gear (which in turn drives a plurality of bevel gears to cause rotation of the axle half shafts). The pinion gears of the forward and rear axle assemblies are driven by an inter-axle differential housed with the forward axle assembly (with the rear axle assembly being driven by the inter-axle differential through the intermediate drive shaft assembly).
The forward axle assembly of the tandem axle assembly and the vehicle transmission are coupled to opposite end of a vehicle drive shaft assembly-typically through fixed end yokes and universal joints. During movement of the vehicle, movement of the rear axle assembly of the tandem axle assembly and movement of the vehicle suspension cause the length of the driveline extending between the transmission and rear axle assembly to vary. In conventional vehicles, this variation in length is accommodated by a splined slip connection within the drive shaft assembly. In particular, the drive shaft typically includes a female member having a plurality of splines and a male member having a corresponding plurality of splines and telescoped within the female member. The two members of the drive shaft are thereby able to move axially relative to one another and accommodate variations in the length of the driveline.
Forming the splined slip connection in the drive shaft assembly is disadvantageous. The drive shaft requires two separate parts and is relatively costly and heavy. Further the spline slip connection renders balancing of the driveshaft and driveline more difficult and increases runout of the driveshaft.
The inventors herein have recognized a need for a tandem axle assembly that will minimize and/or eliminate one or more of the above-identified deficiencies.